This invention relates to polyimides which are prepared from halogenated oxydiphthalic anhydrides. Polyimides are used for various applications including films, coatings, and molded articles. Polyimides are generally characterized by excellent physical properties, such as high heat resistance, high impact strength and wear resistance, and the like. Polyimides are commonly prepared by polycondensation of a dianhydride and a diamine. The properties of polyimides can be varied depending on the specific dianhydride and diamine employed.
A variety of dianhydrides are shown in the literature as monomers in the preparation of polyimides.
U.S. Pat. No. 4,697,023 discloses the preparation of oxydiphthalic anhydrides and suggest their use in the preparation of polyimides. The oxydiphthalic anhydrides are prepared by the reaction of a halophthalic anhydride with water and an alkali metal compound such as KF, CsF, Or K.sub.2 CO.sub.3 in the presence of a polar aprotic solvent.
Kolesnikov, G.S. et al, Vysokomol. Soyed, A9, 612-18 (1967); Marvel, C.S. et al, J. Am. Chem. Soc., 80, 1197 (1958); and Latrova, Z.N. et al, Volokna Sin. Polim., 15-24 (1970) disclose the preparation of oxydiphthalic acids and anhydrides by the oxidation of tetramethyl-diphenyl ethers.
German Patent No. 2,416,594 (1975) discloses the preparation of oxydiphthalic anhydride by coupling of 3-nitrophthalic anhydride in the presence of metal nitrites such as sodium nitride.
U.S. Pat. No. 3,879,428 to Heath et al discloses the preparation of various aromatic bis(ether anhydrides) by reaction of nitrophthalimide with an alkali diphenoxide followed by hydrolysis to yield the diether anhydride.
Scola and Vontell (ChemTech, Feb. 1989, p 112) disclose the preparation of various polyimides, including fluorine-containing polyimides, based on fluorine-containing dianhydrides and/or diamines.
It will be generally appreciated by those skilled in the art that a need exists for a broader selection of polyimides based on the various properties needed for applications in the electrical, electronics, automotive, aerospace, and packaging industries. The polyimides of this invention are based on the use of novel halogenated oxydiphthalic anhydrides, optionally in combination with other anhydrides.